Since electroluminescent (EL) quantum dots (QDs) are considered a key component of the next-generation display, and large-scale production of environment-friendly QDs is required for their wide use in commercial displays. Therefore, several studies on non-cadmium QDs, such as indium phosphide (InP) QDs in the III-V category, graphene QDs, and copper indium sulfide (CuInS2) or silver indium sulfide (AgInS2) QDs in the I-III-VI2 category, have been conducted owing to their non-toxicity and good optical properties. Subsequently, significant results have been reported for green and red colors. However, for synthesis of blue QDs, pure blue emission in the range of 440-460 nm has been achieved with few materials. Among them, zinc selenide (ZnSe) is a promising candidate for synthesizing blue QDs. However, owing to the wide band gap (2.7 eV) of ZnSe, highly effective QDs were attained in the violet region (420-440 nm). Here, for the first time, we have synthesized ZnSe/ZnSexS1-x/ZnS QDs emitting at a wavelength of 444 nm with high photoluminescence quantum yield (PLQY) of 77.2%. Also, full width at half maximum (FWHM) of 23.3 nm ensured its excellent color purity. Use of a gradient intermediate shell of ZnSeS in the original ZnSe/ZnS QDs was the key factor behind this achievement. The intermediate gradient shell of ZnSeS around the core delocalizes the electrons, weakening the quantum confinement effect (QCE), hence rendering the emission color of the QDs tunable from violet to blue by manipulating the ratio of selenium (Se) and sulfur (S) in the composites. A blue emission peak centered at 452 nm was observed for the quantum dot light-emitting diodes (QD-LEDs) fabricated using the above-mentioned QDs, and an external quantum efficiency (EQE) of 5.32%, current efficiency of 1.51 cd/A, and power efficiency of 0.74 lm/W were reported. Furthermore, our fabricated device exhibited a maximum brightness of 3,754 cd/m2 and a half operational time (LT50) with 100 cd/m2 initial luminance of 1.27 h, which are the highest values of these parameters to be reported till date for a blue QD-LED fabricated using ZnSe core based QDs in pure blue region.

中文翻译：

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使用 ZnSe/ZnSexS1-x/ZnS QD 制备高效纯蓝光电致发光器件

由于电致发光 (EL) 量子点 (QD) 被认为是下一代显示器的关键组成部分，因此需要大规模生产环境友好型量子点，才能在商业显示器中广泛使用。因此，一些关于非镉量子点的研究，例如 III-V 类中的磷化铟 (InP) 量子点、石墨烯量子点和 I-III-VI2 中的硫化铜铟 (CuInS2) 或银硫化铟 (AgInS2) 量子点由于它们的无毒和良好的光学特性，已经进行了分类。随后，报告了绿色和红色的显着结果。然而，对于蓝色 QD 的合成，已经用很少的材料实现了 440-460 nm 范围内的纯蓝色发射。其中，硒化锌（ZnSe）是合成蓝色量子点的有希望的候选者。然而，由于 ZnSe 的宽带隙 (2.7 eV)，在紫色区域 (420-440 nm) 中获得了高效的 QD。在这里，我们首次合成了 ZnSe/ZnSexS1-x/ZnS 量子点，其波长为 444 nm，具有 77.2% 的高光致发光量子产率 (PLQY)。此外，23.3 nm 的半峰全宽 (FWHM) 确保了其出色的色纯度。在原始 ZnSe/ZnS QD 中使用 ZnSeS 的梯度中间壳是这一成就背后的关键因素。核心周围 ZnSeS 的中间梯度壳使电子离域，削弱了量子限制效应 (QCE)，从而通过控制中硒 (Se) 和硫 (S) 的比例，使量子点的发射颜色从紫色到蓝色可调复合材料。使用上述 QD 制造的量子点发光二极管 (QD-LED) 观察到以 452 nm 为中心的蓝色发射峰，外量子效率 (EQE) 为 5.32%，电流效率为 1.51 cd/A ，据报道功率效率为 0.74 lm/W。此外，我们制造的设备的最大亮度为 3,754 cd/m2 半运行时间 (LT50)，100 cd/m2 初始亮度为 1.27 小时，这是迄今为止蓝色 QD 报告的这些参数的最高值-在纯蓝色区域中使用基于 ZnSe 核的 QD 制造的 LED。